Pin and sleeve types of electrical connectors have been developed for a variety of special applications and have proven to be extremely useful and advantageous for a number of reasons. The descriptive name for this type of connector is derived from the construction of the male and female connector portion wherein the electrical contacts in the male part, or plug, are two or more cylindrical, solid, electrically conductive pins which are mounted in the body of the plug and the contacts in the female part, or receptacle, are a corresponding number of electrically conductive sleeves. The pins in the plug are surrounded by a substantially cylindrical protective shroud. The receptacle portion of such a connector includes a generally cylindrical insulating inner body having tubular recesses with the elongated conductive sleeves to receive the pins and a shell which is spaced from the insulating body, leaving an annular gap to receive the shroud. The shroud and shell are provided, respectively, with a key and slot so that the orientation of the shroud with respect to the shell, and with respect to the pin-receiving body of the receptacle, is clearly established.
Additionally, the ground pin of the plug portion of the connector is always larger in diameter than the other pins and the conductive sleeve to receive the ground pin in the receptacle body not only is suitably sized to receive the pin but also reaches further toward the open end of the body than the conductive sleeves adapted to receive the other pins, thereby permitting a ground connection to be established before any other electrical connection is made. Of particular importance is the fact that the shroud surrounding the pins is molded plastic and therefore electrically non-conductive, a characteristic which minimizes the possibility of accidentally coming in contact with the pins while joining the connector portions together.
Pin and sleeve connectors have numerous advantages including the fact that the pin arrangements can be made in a variety of configurations, each configuration being unique to a particular set of voltage, phase and current characteristics. The shroud, as mentioned above, protects the pins from damage and protects the user from accidental contact with the pins. Normally, the receptacle carries the power which is supplied to the plug. Thus, the shroud enters the annular cavity in the receptacle before the power is applied to the pins, providing a further safety feature. The shroud construction tends to exclude foreign materials and the overall construction has been found to be highly durable and reliable.
Such connectors do, however, have some disadvantages as found in the prior art. Because of the cylindrical construction characteristics, the connectors tend to be rather long and bulky. The receptacles have required large, special housings in the form of large boxes which are generally mounted either on the surface of a wall or in a special equipment rack. These boxes also protrude from the surface of the wall a considerable distance, i.e., several inches. Special boxes are required and surface wiring is usually used which for many applications is not as desirable as wiring inside the wall. It would be preferable if at least the more common lower current- and voltage-rated receptacles could be mounted in standard two-gang wall outlet boxes.
Typically, pin and sleeve receptacles of the prior art have mounting flanges which are positioned at a substantial distance from the front face of the receptacle, i.e., an inch or so toward the rear of the outer housing or shell of the receptacle, in order to be able to accommodate hinged covers and the like to close the front of the receptacle when the plug is not plugged into the receptacle and/or to lock the plug to the receptacle against removal. Thus, in addition to the other structural characteristics of the connector which require special boxes, the flange position contributes to the protruding characteristics of the receptacle and the resultant plug-receptacle connective assembly. Characteristically, the receptacle protrudes considerably further from the surface of the electrical outlet box on which it is mounted that its corresponding flat blade counterpart receptacles.
These disadvantages render the use of such connectors unacceptable in many installations where they would otherwise be highly desirable, particularly in work areas in which people frequently must pass close to a wall area.